Nicholas Fifield was originally charged with third-degree sex abuse of an 18-year-old mentally ill woman. (Facebook)

An Iowa high school tennis star accused of sexually assaulting a mentally ill woman may walk away with probation after pleading guilty to a lesser charge, authorities said.

Nicholas Fifield was 17 when he was charged in December with third-degree sex abuse of a person “suffering from mental defect or incapacity, which precludes giving consent.”

Fifield picked up the 18-year-old victim, who he met through an online dating site, on December 5 after promising to her parents and the staff at her Des Moines group home that they would be going to the movies, the Des Moines Register reported.

Fifield was hit with a one-tennis-match suspension after he was charged. The son of West Des Moines high school tennis coach Jay Fifield, he went on to play doubles at the state tennis tournament in May, according to reports.

Fifield, now 18, was scheduled to go on trial August 16, but he entered an Alford plea to a lesser charge of assault with intent to commit serious injury, meaning he admitted no guilt but acknowledged there was enough evidence to convict him.

Polk County Attorney John Sarcone said his office will not oppose probation with possible treatment for Fifield, a first-time offender.

“That’s agreeable with the victim’s family,” Sarcone told the Register. “It’s two people with a lot of issues between them. We are trying to resolve it in a way that’s good for all. Prison would not do this kid any good.”

He will be sentenced on October 12 by Judge William Patrick Kelly after a mental evaluation and pre-sentence investigation.